Many manufacturers routinely perform inspection on their manufactured products. This is typical of quality control measures where products that are defective are identified so as to control the quality of the manufactured products.
Many manufactured products require inspection on the products' interior surfaces, such as nut holes. Conventional methods of performing a hole inspection typically involve the use of a camera for capturing an internal surface of the hole. The camera and the manufactured product are usually rotated with respect to each other in order to obtain a complete all round view of the internal surface.
In many cases, the camera and the manufactured product are rotated by three hundred and sixty degrees relative to each other. The camera subsequently captures the complete all round view of the internal surface as the camera or product completes the rotation. The captured image of the interior of the manufactured product is then used to identify potential defects on the interior of the product.
However, the conventional methods of performing hole inspection are undesirably time consuming due to the time required for rotating the camera with respect to the manufactured product.
Additionally, the conventional methods of performing hole inspection are costly to implement because a rotating mechanism is required for rotating the manufactured product. The rotating mechanism also produces vibration that undesirably affects the quality of images obtained by the conventional methods.
Furthermore, conventional systems for performing hole inspection do not possess sufficient depth of focus. This results in defocusing of hole images captured by the conventional systems, and produces undesirable low quality images or unfocussed images. Unfocussed images are difficult to inspect as well as to extract crucial dimensional information because calibrating the unfocussed images results in poor pixel resolution characteristics.
FIGS. 6a and 6b depicts prior art systems for hole inspection. With reference to FIG. 6a, an optical system 600 consisting of a camera 602 and an optical module 604 is mounted on a rotary mechanism (not shown) that rotates around a central axis 606. A rotary table (not shown) moves the optical module 604 to three different positions 1,2,3 where three images, namely image 1, image 2 and image 3 of an object 608 are captured. An illuminator 609 is used to illuminate the object 608. Depending on the purpose of the inspection or the object to be inspected, more of such positions can be setup to obtain more images. These images are subsequently inspected by a controller 610 that identifies defects in each of these images and determines if the object 608 is good or faulty by comparing inspected parameters with a golden template or through measurements of defects against limits set by end users.
FIG. 6b depicts another prior art system 700 wherein the object 608 is rotated instead of the optical module 604. This prior art system 700 is normally used for inspecting objects that have small to medium size and weight or in cases where the optical module cannot be rotated due to spatial or design limitations. In this prior art system, the object 608 is rotated while the optical module 604 captures images of the object 608 at several preset intervals to produce the same effect as the prior art system 600 of FIG. 6a. 
In the foregoing prior art systems 600, 700, the time required to capture several images is not only undesirably long, the controller 610 is also required to process several images to produces images for inspection. Additionally the system cost of the foregoing prior art systems is undesirably high due to the need to use a motor and encoder module 612 to rotate the optical module 604 or the object 608. Information on the rotation of the optical module 604 or the object 608 is then fed back to the controller 610 for triggering the cameras 602 at appropriate trigger preset points.
There is therefore a need for inspecting internal surfaces of a hole in an object without requiring the object to be rotationally displaced and quickly arrive at a result by inspecting a single image of the entire internal surfaces of the hole.